1. Field of the Invention
The present invention relates to a cylinder identifying device for an internal combustion engine which identifies cylinders from one series of signals of a rotary signal generator.
2. Discussion of the Background
In controlling an ignition timing or a fuel injection timing of an internal combustion engine, it is necessary to identify cylinders and therefore, signals in synchronism with rotation of an engine are employed. This signal generator normally detects rotation of a cam shaft or a crank shaft. FIG. 4 and FIG. 5 show an example of such a rotary signal generator which is used in an internal combustion engine having four cylinders.
In FIGS. 4 and 5, numeral 1 designates a rotating shaft which rotates in synchronism with the engine, numeral 2 designates a rotating disc which is attached to the rotating shaft 1, wherein four windows 3 corresponding to the respective cylinders are provided at its outer peripheral side, and one window 3 corresponding to a specific cylinder is provided at its inner peripheral side. Numeral 4 designates light emitting diodes installed in correspondence with the windows 3 at the outer peripheral side of the rotating disc 2 and the window 3 at the inner peripheral side thereof, numeral 5 designates photodiodes which receive output beams from the light emitting diodes 4, respectively, numeral 6 designates an amplifying circuit which is connected to each photodiode 5 and amplifies an output signal of the photodiode 5, and numeral 7 designates an output transistor having an open collector which is connected to the amplifying circuit 6. Further, although only the circuit having a pair of the light emitting diode 4 and the photodiode 5 is exemplified in FIG. 5, there naturally installed is another similar circuit.
Next, an explanation will be given of the operation based on signal waveform diagrams shown in FIGS. 6(a) and 6(b). With the rotation of the internal combustion engine, a crank angle reference signal (SGT) shown in FIG. 6(b), which corresponds to light emitted by the light emitting diode 4 and received by the photodiode 5 at the outer peripheral side, is output from transistor 7 and a cylinder identifying signal (SGC) shown in FIG. 6(a), which corresponds to light emitted by the light emitting diode 4 and received by the photodiode 5 at the inner peripheral side, is output from transistor 7.
In this structure, the crank angle reference signal (SGT) is a signal which reverses by a predetermined crank angle of each cylinder, and which is employed as a reference signal of the crank angle with respect to each cylinder. Further, the cylinder identifying signal (SGC) outputs a signal in synchronism with the generation of the crank angle reference signal (SGT) corresponding to #1 cylinder, which is used to identify the #1 cylinder. Accordingly, by detecting the timing of the specific cylinder (#1 cylinder in FIG. 6(a)) by the cylinder identifying signal (SGC), it is possible to successively identify all the cylinders.
As shown in FIG. 7, the output signals of the rotary signal generator 8 are inputted to a microcomputer 10 via an interface circuit 9, and are employed in calculations for controlling the ignition timing, the fuel injection and the like in correspondence with the respective cylinders.
In the conventional cylinder identifying device for an internal combustion engine, it is necessary to generate two series of signals in the rotary signal generator to obtain the crank angle reference signal (SGT) and the cylinder identifying signal (SGC), and therefore, the construction is complicated which brings about a high cost.
Further, methods for identifying cylinders by one series of signals are disclosed in Japanese Unexamined Patent Publication No. 12138/1991 and Japanese Unexamined Patent Publication No. 12139/1991. However, there are problems in both publications wherein erroneous identification of cylinders is apt to cause when there are a fabrication error in positional signals and a rotational variation of an engine.